UPS Ever Duo II Pro with NUT / Linux – bad idea

In my previous post about that device I described UPS Ever Duo II Pro working with nut under Linux, along with variables it exports, battery charge and drain cycles and this UPS’ issues. This follow-up is why using this UPS for serious unattended production environment is not a good idea.

As mentioned before, I have discovered and confirmed (two devices of the same model in a row) that the device has two major flaws:

Does not always indicate LB status to the host despite audible fast-beeping

Can easily be rendered unusable with completely fair (non-hackish) combination of commands and real-life circumstances

Just to recap – here’s the scenario an UPS is designed for and should honor (aside from situations when the user is just there to act appropriately):

Power is on, status OL, host system is running

Power goes out, status OB, host system notified and running (normally or with reduced activities)

Power is out, status LB, host system shuts down to a halt and commands the UPS to turn off and come back on when the power is back

Power is out, system is down, UPS is off

Power comes back, UPS goes OL, system boots

At any time the power may suddenly come back:

at [2] until [3] – system running, forced shutdown not initiated, coming OL, notified, resuming any heavy-duty activities if suspended before

at [3] until [5] – forced shutdown started, in progress or finished; to bring the system up there is no other way now than to run the whole power-off/power-on cycle – otherwise it will just stay halted after shutdown

The first flaw (no LB indication) may hit you at [2] unless you trust blazer driver’s calculations along with clone driver workaround. The timing might be wrong after some time (battery degradation) causing the obvious.

The second flaw is much more serious. If you are at or after [3] the power may come back at any moment, and the UPS must still honor the shutdown command and shut the load off, wait, and come back. Ever Duo II Pro does not and will leave you “with your pants down” to say colloquially. It will not shut down when OL, but after a single shutdown command in OL it will be shutting down every time it goes OB and there’s no way I have discovered to revert it to a sane state. It means that it will basically stop doing its main job. Additionally when in that lock-up state – it reports false values (i.e. ups.load stuck at 11 but nothing connected) for its variables and I am pretty convinced both flaws are a firmware issue.

If I remember correctly I have had this issue already about 10 years ago with a different Megatec-compatible UPS device. Looks like the firmware is buggy for ages and seems not to be fixed even today.

To summarize: Avoid this UPS for unattended production environments. And pay attention to any other Megatec-compatible UPS you get, the firmware may be at least 10 years old, unmaintained and with major bugs. On the personal side – I am tired of the situation with poor UPS-es and probably will be heading for a proven APC-Smart (unfortunately much more expensive).

I had an option to return the device, so in fact did not bother to work out these issues with the manufacturer. UPS business itself is quite specific – a customer buys one to feel safe, tests it once to see it going on/off-battery, and then usually does not test any full scenario it until an outage happens, so most smaller vendors just don’t care too much. The warranty period often ends before an critical outage, and that’s it.

Not sure whether they supply a Linux client software, but my fair guess is that id would be a clumsy closed source binary anyway (some years ago there was UPSILON). Note that Megatec protocol by itself supports rather limited amount of data (see http://www.networkupstools.org/ups-protocols/megatec.html) – no runtime, etc. Finally, the forever-off bug has been reproduced by me with two units, the same way. That was the bottom line to the fact I returned it, however the unit might be good for a non-unattended office/desktop environment.

Of course you might try resolving these issues with the manufacturer – I saved myself grey hair and went with a refurbished unit from well known UPS brand, described in my other posts😉

Thank you for sharing your observations regarding cooperation of DUO II Pro UPS with NUT on your blog. It is a pity that you did not contact EVER, as we are working currently on integrating part of EVER UPSs with NUT software.

We are currently checking issues reported in your post above.

BTW: Why do you block entering your blog from our company IPs. I had to use Anonymizer to get here.

It’s great to hear that you are working on integrating with nut (despite the fact, that it’s actually working, or at least very much seems to). Note that I am pointing to a possible firmware issue though, which would then seem to be the area you should focus primarily on – unless you decide to change the communications protocol, which basically also means tackling the firmware. Unless there’s no firmware and it’s some kind of FPGA logic, etc.

Nevertheless would you please put a comment when it’s fixed, so the readers know. Just sharing my neutral observations.

Ad BTW – I am not blocking anyone🙂 My recommendation – check the issue with your company’s IT policy; you might be breaking it right now if your CIO decided to block wordpress.com sites and you breach it using Anonymizer.